Chemical properties describe how a substance interacts with other substances. For example, flammability, toxicity, and reactivity are all chemical properties. Colorless gas is a chemical property because it describes how a substance interacts with light. When light hits an object, some of the light is absorbed and some is reflected. The color of an object is determined by the wavelengths of light that are reflected. A colorless gas is a gas that does not absorb any visible light, so it reflects all of the light that hits it. This means that a colorless gas appears invisible to the human eye.